JP5931603B2 - Gas sensor - Google Patents

Description

  The present invention relates to a gas sensor.

  As a gas sensor for detecting a specific gas component in a gas to be measured, a sensor having a sensor element whose electrical characteristics change according to the concentration of the specific gas component in the gas to be measured has been known (Patent Documents 1 to 1). 6). Examples of such sensor elements include a bottomed cylindrical solid electrolyte with a closed tip, an inner electrode (reference electrode) formed on the inner surface of the solid electrolyte, and a tip of the outer surface of the solid electrolyte. A sensor element is known that includes a formed outer electrode (detection electrode) and a lead portion formed to extend from the outer electrode to the rear end side on the outer surface of the solid electrolyte. When incorporating such a sensor element into a gas sensor, for example, a connection terminal fitting connected to a lead wire provided in the gas sensor is prepared in order to extract a detection signal from the gas sensor. Is inserted. For example, in order to connect the lead wire and the outer electrode of the sensor element, it is only necessary to fit the connection terminal fitting to the outer surface of the rear end portion of the sensor element, whereby the lead is connected via the connection terminal fitting and the lead portion. The wire and the outer electrode are electrically connected.

  In the connection terminal fitting as described above, a cylindrical portion that is elastically deformable in the radial direction is generally provided at the tip portion as a structure for fitting on the outer surface of the rear end portion of the sensor element. The cylindrical portion is smaller in diameter than the rear end portion of the sensor element before being fitted into the sensor element (non-fitted state), and the cylindrical portion is fitted into the outer surface of the rear end portion of the sensor element. In this case, the diameter of the cylindrical portion is increased in the radial direction so as to ride on the sensor element. Therefore, in such a cylindrical part, in order to facilitate the operation of fitting the cylindrical part into the rear end part of the sensor element, the diameter-enlarging part that expands toward the front end at the front end part of the cylindrical part. The structure which provides is proposed (for example, refer to the collar part 62f of Patent Document 1). By making the diameter of the tip of the enlarged diameter part larger than the diameter of the rear end (rear end part) of the sensor element, the rear end part of the sensor element can be easily guided into the cylindrical part following the enlarged diameter part. The fitting operation becomes easy.

JP 2010-25731 A JP 2010-181347 A JP 2009-281727 A JP 2008-286810 A Japanese Patent Laid-Open No. 2004-205341 JP 2009-2846 A

  However, there has been a case where it is not possible to sufficiently meet the demand for downsizing the sensor element by reducing the axial length of the sensor element. In recent years, a configuration for reducing the amount of wiring material (for example, precious metal) used for electrodes and leads has been studied, and the lead portion formed on the rear end side by shortening the rear end portion of the sensor element. As a result, the amount of wiring material used can be reduced. By the way, in a gas sensor, the structure which arrange | positions a metal member (metal fitting) so that a sensor element may be surrounded, and a sensor element protrudes from the rear-end part of a metal fitting may be employ | adopted. In this case, if the length of the rear end portion of the sensor element is shortened in order to reduce the amount of wiring material used, the length of the rear end portion of the sensor element protruding from the metal shell is shortened. As a result, in order to maintain the reliability of the electrical connection between the sensor element and the connection terminal metal fitting, when trying to fit the cylindrical part closer to the front end side, the diameter larger than the diameter of the rear end part of the sensor element is increased. There may be a problem that the expanded metal portion and the metal shell come into contact with each other to cause a short circuit between the metal shell and the connection terminal metal fitting. Moreover, in order to avoid such a short circuit, if the fitting amount of the cylindrical part to the sensor element is suppressed, there may be a problem that the reliability of electrical connection between the sensor element and the connection terminal fitting is lowered. Furthermore, it has been difficult to adjust the diameter of the enlarged diameter part so as not to contact the metal shell while making the diameter of the enlarged diameter part larger than the diameter of the rear end part of the sensor element.

  The present invention has been made to solve the above-described conventional problems, facilitates the operation of fitting the connection terminal fitting into the sensor element without complicating the manufacturing process, and the sensor element and the connection terminal fitting. The purpose is to ensure the reliability of the electrical connection.

  The present invention has been made to solve the above-described problems, and can be implemented as the following forms or application examples.

[Application Example 1]
A cylindrical sensor element that extends in the axial direction, and includes an outer electrode provided on the outer surface of the tip, which is one end in the axial direction, and the other end in the axial direction from the outer electrode. An external lead portion provided to extend to the outer surface on the rear end side that is a portion, and a sensor element,
A cylindrical portion that is elastically deformable in a radial direction, and at least a tip end portion of the cylindrical portion is fitted into an outer surface of a rear end portion of the sensor element, and contacts the external lead portion in the cylindrical portion A terminal,
In a gas sensor for detecting a specific gas component in a gas to be measured, comprising:
The rear end portion of the sensor element has an outer diameter larger than the inner diameter of the cylindrical portion when the sensor element is not fitted into the sensor element, and the cylindrical portion is fitted into the sensor element when the cylindrical portion is fitted into the sensor element. A base portion in contact with the inner surface of the base portion, and a shrinkage formed on the rear end side of the base portion and having an outer diameter on the rear end side that is at least smaller than the inner diameter of the cylindrical portion when in the non-fitted state. With a diameter part,
A gas sensor, wherein a rear end of the external lead portion on the outer surface of the sensor element is disposed on a boundary between the base portion and the reduced diameter portion.

  According to the gas sensor of Application Example 1, since the sensor element rear end portion includes the reduced diameter portion whose outer diameter on the rear end side is at least smaller than the inner diameter of the cylindrical portion in the non-fitted state, the sensor element is contracted. By following the diameter of the cylindrical portion, the rear end portion of the sensor element can be easily guided into the cylindrical portion, and the operation of fitting the connection terminal into the sensor element can be facilitated and performed more accurately. It becomes possible. By accurately fitting the connection terminal into the sensor element, the reliability of the electrical connection between the connection terminal and the outer electrode can be maintained. Furthermore, since it is not necessary to make the diameter of the enlarged portion larger than the diameter of the rear end portion of the sensor element, it is only necessary to adjust the diameter of the enlarged portion so as not to contact the metal shell. Adjustment is easy.

  In addition, when the connection terminal is fitted into the sensor element so that the cylindrical portion follows the reduced diameter portion of the sensor element while the reduced diameter portion is formed in the sensor element, the cylindrical portion is fitted to the base portion of the sensor element. In this case, the tip side of the cylindrical part may float (separate) from the base part of the sensor element, and the reliability of the electrical connection between the connection terminal and the outer electrode (external lead part) decreases. Sometimes. On the other hand, according to the gas sensor of Application Example 1, the rear end of the external lead portion is disposed on the boundary between the base portion and the reduced diameter portion on the outer surface of the sensor element. Even if the tip side floats from the base part of the sensor element, the cylindrical part surely comes into contact with the boundary between the base part and the reduced diameter part, and the electrical connection between the outer electrode and the connection terminal is made. Reliability can be secured.

[Application Example 2]
The gas sensor according to Application Example 1, wherein the cylindrical portion is provided at the forefront of the connection terminal.

  According to the gas sensor described in Application Example 2, since the cylindrical portion is provided at the forefront of the connection terminal, it is necessary to provide an enlarged diameter portion whose diameter increases toward the distal end at the distal end portion of the cylindrical portion of the connection terminal fitting. Since there is no need to perform special processing on the connection terminal, it is possible to suppress complication of the manufacturing process of the connection terminal. In addition, it is not necessary to adjust the diameter of the enlarged diameter portion, and the reliability of electrical connection between the connection terminal and the outer electrode can be easily maintained.

[Application Example 3]
The gas sensor according to Application Example 1 or 2, further including a metal shell that surrounds the sensor element and exposes at least the reduced diameter portion of the sensor element, and is fitted into a rear end portion of the sensor element. A gas sensor in which a tip part of a cylindrical part is arranged in the metallic shell.

  According to the gas sensor described in Application Example 3, even if the rear end portion of the sensor element is formed to be shorter by inserting the tip of the cylindrical portion into the metal shell, the sensor element and the cylindrical portion are in the axial direction. It is possible to secure a sufficient distance to overlap. Therefore, while maintaining the reliability of the electrical connection between the connection terminal and the outer electrode, the sensor element can be formed shorter and the gas sensor can be downsized. As a result, by shortening the rear end portion of the sensor element, the amount of wiring material used for forming the external lead portion and the like can be suppressed. In addition, since the cylindrical portion is provided at the forefront of the connection terminal without providing an enlarged diameter portion as in the prior art, the tip of the cylindrical portion is mainly used without short-circuiting the metal shell and the connection terminal metal fitting. It becomes possible to arrange | position in a metal fitting.

[Application Example 4]
The gas sensor according to Application Example 1 or 2, further comprising a metal shell that surrounds the sensor element and exposes a rear end portion of the sensor element, and the cylindrical portion has a slit parallel to the axial direction. The slit can be elastically deformed in the radial direction by expanding and contracting the width of the slit, and the rear end portion of the external lead portion has the boundary between the base portion and the reduced diameter portion as a rear end. A ring lead portion extending on a part of the outer surface of the sensor element along an outer periphery of the sensor element; and the sensor element is surrounded by the metal shell so that the ring lead portion is exposed from the metal shell. Gas sensor.

  According to the gas sensor described in Application Example 4, the ring lead portion extends to a part of the outer surface of the sensor element along the outer periphery of the sensor element. Thereby, compared with the case where a ring lead part is provided in the perimeter along the outer periphery of the sensor element of the outer surface of a sensor element, the length of a ring lead part becomes short, As a result, the usage-amount of wiring material can be reduced. In addition, since the ring lead portion is exposed from the metal shell, when the cylindrical portion of the connection terminal is fitted into the rear end of the sensor element, the position of the ring lead portion is confirmed from the outside of the metal shell, The positional relationship between the cylindrical portions can be adjusted. Therefore, even if the ring lead portion is provided along a part of the outer periphery of the sensor element and the cylindrical portion has a slit, the reliability of the electrical connection between the cylindrical portion and the ring lead portion is improved. Can be maintained.

[Application Example 5]
The gas sensor according to any one of Application Examples 1 to 4, wherein the reduced diameter portion includes a small diameter portion having a constant outer diameter that is smaller than an inner diameter of the cylindrical portion when the sensor portion is not fitted in the sensor element. A gas sensor comprising a step portion formed between the base portion and the small diameter portion.

  According to the gas sensor described in Application Example 5, when the cylindrical portion is fitted into the rear end portion of the sensor element, the small diameter portion is easily guided into the cylindrical portion. And the front-end | tip of a cylindrical part is guide | induced to the base | substrate part, after contact | abutting to a level | step-difference part, and the operation | movement of insertion can be performed easily and correctly.

[Application Example 6]
5. The gas sensor according to any one of Application Examples 1 to 4, wherein the reduced diameter portion is a tapered portion that gradually decreases in outer diameter from a boundary with the base portion toward a rear end of the sensor element.

  According to the gas sensor described in Application Example 6, when the cylindrical portion is fitted into the rear end portion of the sensor element, the rear end of the reduced diameter portion is easily guided into the cylindrical portion. Then, after the tip of the cylindrical portion abuts at a position in the middle of the taper portion, the tip is guided to the base portion by the taper portion, and the fitting operation can be performed easily and accurately.

  The present invention can be realized in various forms other than those described above. For example, the present invention can be realized in a form such as a gas sensor manufacturing method.

2 is a cross-sectional view illustrating a configuration of a gas sensor 100. FIG. 1 is a perspective view illustrating an appearance of a sensor element 10. FIG. 4 is a perspective view illustrating an appearance of a second connection terminal 80. FIG. It is explanatory drawing which shows the outline | summary of the assembly of the gas sensor. 4 is an explanatory diagram illustrating a state where a tubular portion 83 is fitted into the sensor element 10. FIG. 2 is a perspective view illustrating an appearance of a sensor element 110. FIG.

A. Configuration of the gas sensor 100 of the first embodiment:
FIG. 1 is a sectional view showing the configuration of a gas sensor 100 as a first embodiment according to the present invention. As shown in FIG. 1, the gas sensor 100 has an elongated shape that extends along the axis O. In the following description, the lower side in FIG. 1 in the direction of the axis O is referred to as the front end side, and the upper side in FIG. 1 is referred to as the rear end side. The gas sensor 100 of the present embodiment is an oxygen concentration sensor, and can be used, for example, to detect the oxygen concentration in the exhaust gas of an automobile.

  The gas sensor 100 includes a sensor element 10, a metal shell (housing) 20, an outer cylinder 40, and a structure (electrode and wiring connected to the electrode) related to routing of the internal wiring of the gas sensor as main components. ing. The sensor element 10 constitutes an oxygen concentration cell in which a pair of electrodes are laminated on both surfaces of an oxide ion conductive (oxygen ion conductive) solid electrolyte body, and outputs a detected value corresponding to the oxygen partial pressure. It is a sensor element. Specifically, the sensor element 10 includes a bottomed cylindrical solid electrolyte body 11 whose outer diameter is tapered toward the tip, and inner electrodes formed on the inner surface and the outer surface of the solid electrolyte body 11, respectively. (Reference electrode) 10a and outer electrode (detection electrode) 10b. Then, the inner space of the sensor element 10 is set as a reference gas atmosphere, and the gas to be detected is brought into contact with the outer surface of the sensor element 10 to detect the gas. From the rear end of the gas sensor 100, two lead wires 60 for taking out the detection signal of the sensor element 10 are drawn out.

  FIG. 2 is a perspective view showing the appearance of the sensor element 10. The sensor element 10 is formed with a flange 12 protruding (protruding) in the outer peripheral direction in the middle of the axis O direction. A bottomed portion 13 that is gradually reduced in diameter toward the distal end side and closed at the distal end portion is formed on the distal end side of the flange portion 12. In the present embodiment, the outer electrode 10 b is formed so as to cover a part of the outer surface of the bottomed portion 13. Further, the outer electrode 10b is covered with an electrode protective layer 14 for protecting the outer electrode 10b.

  The sensor element 10 is provided on the rear end side of the flange portion 12 on the cylindrical base portion 17 having a substantially constant outer diameter, and on the rear end side of the base portion 17, and has an outer diameter smaller than that of the base portion 17. And a reduced diameter portion 18 formed. Here, the reduced diameter portion 18 forms an opening at the rear end of the sensor element 10, and has a small diameter portion 18a having a constant outer diameter smaller than the outer diameter of the base portion 17, and the base portion 17 and the small diameter portion 18a. And a stepped portion 18b having an outer diameter that smoothly changes between the base portion 17 and the small-diameter portion 18a.

  In addition, the outer lead portion 10c electrically connected to the outer electrode 10b is provided on the outer surface on the rear end side of the flange portion 12 and the flange portion 12. The external lead portion 10c of the present embodiment is a vertical lead extending linearly in the direction of the axis O from the rear end portion of the outer electrode 10b via the flange portion 12 to the rear end side of the flange portion 12. And a ring lead portion 16 provided at the rear end of the vertical lead portion 15. The ring lead portion 16 extends to a part of the outer surface of the sensor element 10 along the outer periphery of the sensor element 10 with the boundary between the base portion 17 and the reduced diameter portion 18 as the rear end. The configuration of the reduced diameter portion 18 and the ring lead portion 16 described above is a configuration relating to the connection between the outer electrode 10b and the lead wire 60, and will be described in detail later.

  As described above, the inner electrode 10 a is provided on the inner surface of the sensor element 10. A cylindrical hole 10d is formed inside the bottomed cylindrical solid electrolyte body 11 (see FIG. 1), and the inner electrode 10a is formed so as to cover the entire surface of the cylindrical hole 10d except for the vicinity of the rear end. ing.

The solid electrolyte body 11 included in the sensor element 10 can be made of, for example, zirconium oxide (ZrO ₂ ) added with yttrium oxide (Y ₂ O ₃ ), that is, yttria-stabilized zirconia. Alternatively, by other solid electrolyte such as stabilized zirconia to which an oxide selected from calcium oxide (CaO), magnesium oxide (MgO), cerium oxide (CeO ₂ ), aluminum oxide (Al ₂ O ₃ ) and the like is added. The sensor element 10 may be configured.

  The inner electrode 10a and the outer electrode 10b formed on the surface of the sensor element 10 are preferably formed of a noble metal or a noble metal alloy such as platinum (Pt) or a platinum alloy. The inner electrode 10a and the outer electrode 10b can be formed by a plating method such as electroless plating, for example. The external lead portion 10c is formed by, for example, printing a predetermined pattern using a noble metal paste on the outer surface of the molded body of zirconia powder containing yttria as described above when the solid electrolyte body 11 is manufactured. Can be formed simultaneously with the baking.

  Returning to FIG. 1, the sensor element 10 described above is assembled in the metal shell 20. The metal shell 20 is a metal member that is arranged so as to surround the middle part of the sensor element 10 in the axis O direction. On the inner surface of the metal shell 20, a step portion 20b whose inner diameter is reduced toward the distal end is provided. A packing 30 is disposed between the stepped portion 20b and the flange portion 12 of the sensor element 10. When the metal shell 20 and the sensor element 10 are assembled, the sensor element 10 is inserted into the metal shell 20 from the rear end side of the metal shell 20. Then, the flange portion 12 of the sensor element 10 is indirectly brought into contact with the step portion 20 b by applying the flange portion 12 to the packing 30.

  When the metal shell 20 and the sensor element 10 are assembled, a cylindrical sealing material (talc powder) 31 is further inserted in the radial gap between the sensor element 10 and the metal shell 20 on the rear end side of the flange portion 12. Filled. A cylindrical insulating member (ceramic sleeve) 32 is disposed on the rear end side of the sealing material 31. Further, a metal ring (stainless steel flat washer) 33 is disposed on the rear end side of the insulating member 32. Thereafter, the rear end portion of the metal shell 20 is bent inward to form the crimped portion 20a, whereby the insulating member 32 is pressed against the distal end side to crush the sealing material 31, and the insulating member 32 and the sealing material 31 are While being fixed by caulking, the gap between the sensor element 10 and the metal shell 20 is sealed. When the metal shell 20 and the sensor element 10 are assembled as described above, the rear end portion of the sensor element 10 protrudes from the rear end (caulking portion 20a) of the metal shell 20, and the above-described ring lead portion 16 (FIG. 2). Is exposed from the metal shell 20 to the outside.

  In the vicinity of the center of the metal shell 20, a polygonal flange portion 20c formed in a shape protruding radially outward is provided in order to engage a hexagon wrench or the like. A male screw portion 20d is formed on the outer surface between the flange portion 20c and the tip portion 20f that is the tip portion of the metal shell 20. The male screw portion 20d of the metal shell 20 is attached to, for example, a screw hole of an exhaust pipe of an automobile, and the tip of the sensor element 10 is exposed in the exhaust pipe, whereby oxygen in a gas to be detected (exhaust gas) using the gas sensor 100 is exposed. The concentration can be detected. In the gas sensor 100, a gasket for preventing gas escape when the gas sensor 100 is attached to the exhaust pipe is further fitted into the step between the front end surface of the flange portion 20 c and the rear end of the male screw portion 20 d (FIG. Not shown).

  A cylindrical protector 62 made of metal (such as stainless steel) is fixed to the distal end portion 20 f of the metallic shell 20, and the distal end of the sensor element 10 protruding from the metallic shell 20 is covered with the protector 62. The protector 62 has a plurality of holes for taking exhaust gas into the protector 62.

  On the other hand, a metal cylindrical outer cylinder 40 is joined to the rear end portion of the metal shell 20 to cover the rear end portion of the sensor element 10. The outer cylinder 40 can be formed of stainless steel such as SUS430, SUS304, SUS304L, SUS310S, SUS316, SUS316L, or the like. The outer cylinder 40 has a front end portion 40a connected to the metal shell 20, and a rear end portion 40b having a diameter smaller than that of the front end portion 40a. A stepped portion 43 is provided between the front end portion 40a and the rear end portion 40b. Is provided.

  On the inner side of the distal end portion 40a of the outer cylinder 40, a substantially cylindrical and insulating separator 34 with a step is disposed. The separator 34 is formed with two insertion holes 34 a and 34 b that penetrate the separator 34 in the direction of the axis O. The plate-like base portion 71 of the first connection terminal 70 and the plate-like base portion 81 of the second connection terminal 80 are inserted through these insertion holes 34a and 34b, respectively. Here, the first connection terminal 70 and the second connection terminal 80 are members for connecting the inner electrode 10a or the outer electrode 10b and the lead wire 60, respectively. Connection end portions 72 and 82 are formed at the rear ends of the respective plate-like base portions 71 and 81, and different lead wires 60 are caulked and connected to the connection end portions 72 and 82, respectively. The second connection terminal 80 corresponds to a “connection terminal” in the claims.

  The separator 34 has the rear end surface of the separator 34 in contact with the stepped portion 43 of the outer cylinder 40, and the front end surface of the separator 34 is in contact with the holding metal fitting 35 disposed on the front end side of the separator 34. It is held in the tube 40. The holding metal fitting 35 is disposed on the front end side of the separator 34 and is fixed in the outer cylinder 40 by crimping the front end portion 40 a of the outer cylinder 40.

  In the first connection terminal 70, an insertion portion 73 that is inserted into the cylindrical hole 10 d of the sensor element 10 is provided on the distal end side of the plate-like base portion 71. The insertion portion 73 is in contact with the inner surface of the sensor element 10 and is electrically connected to the inner electrode 10a.

  FIG. 3 is a perspective view showing the appearance of the second connection terminal 80. As described above, the second connection terminal 80 includes the connection end portion 82 to which the lead wire 60 is connected and the plate-like base portion 81 disposed in the insertion hole 34 b of the separator 34. A support arm 84 is formed at the center of the plate-like base 81 by forming a cut in a substantially U-shape and bending the inner part thereof toward the outer peripheral side. The support arm 84 supports the plate-like base 81 in the insertion hole 34b of the separator 34 so that the plate-like base 81 is substantially parallel to the axis O direction.

  Further, in the second connection terminal 80, a cylindrical portion 83 is provided on the tip side of the plate-like base portion 81. The cylindrical portion 83 is electrically connected to the outer electrode 10b by being fitted on the outer surface of the sensor element 10 and in contact with the external lead portion 10c. More specifically, the cylindrical portion 83 is formed in a substantially hollow cylindrical shape obtained by bending a substantially rectangular plate, and has a slit 85 parallel to the axis O direction. The cylindrical portion 83 can be elastically deformed in the radial direction by expanding and contracting the width of the slit 85. The operation of fitting the cylindrical portion 83 into the sensor element 10 will be described in detail later.

  Returning to FIG. 1, a substantially columnar grommet 36 is inserted and fixed by caulking inside the rear end portion 40 b of the outer cylinder 40 of the gas sensor 100. The grommet 36 is formed with two insertion holes penetrating the grommet 36 in the direction of the axis O, and the lead wire 60 is drawn out from each of the two insertion holes. The rear end side of the grommet 36 is expanded in a flange shape. The grommet 36 is positioned by inserting the grommet 36 from the rear end of the outer cylinder 40 into the outer cylinder 40 and bringing the above-mentioned enlarged diameter portion into contact with the rear end of the outer cylinder 40. The grommet 36 can be formed of a rubber material such as silicon rubber or fluorine rubber, for example.

  Further, on the side surface of the rear end portion 40b of the outer cylinder 40, four first vent holes 41 (only three are shown in FIG. 1) are arranged at equal intervals in the circumferential direction at a position closer to the tip side than the grommet 36. It is open. An annular air-permeable filter 37 is covered on the radially outer side of the rear end portion 40b of the outer cylinder 40 so as to cover the first ventilation hole 41. Further, the filter 37 is made of a metal cylinder from the radially outer side. A protective outer cylinder 38 is enclosed. The protective outer cylinder 38 can be formed of stainless steel such as SUS430, SUS304, SUS304L, SUS310S, SUS316, SUS316L, or the like. Four second vent holes 39 (only two are shown in FIG. 1) are opened at equal intervals in the circumferential direction on the side surface of the protective outer cylinder 38 so that outside air can be introduced into the outer cylinder 40 through the filter 37. It has become. The filter 37 is held between the outer cylinder 40 and the protective outer cylinder 38 by crimping the outer cylinder 40 and the protective outer cylinder 38 at the front end side and the rear end side of the second vent hole 39. The filter 37 can be constituted by a porous structure of a water repellent resin such as a fluorine-based resin, and has a water repellency, so that the reference gas (in the internal space of the sensor element 10 does not pass through outside water). Air) can be introduced.

  The protective outer cylinder 38 is bent radially inward so that the rear end portion is provided on the rear end surface of the grommet 36, and an opening 63 is formed in the center of the rear end portion. 60 is pulled out. Further, the rear end side of the protective outer cylinder 38 is caulked and fixed to a caulking portion provided at the rear end portion 40 b of the outer cylinder 40. That is, the grommet 36 is disposed in the outer cylinder 40 by simultaneously caulking both the protective outer cylinder 38 and the outer cylinder 40.

B. Outline of assembly of the gas sensor 100:
FIG. 4 is an explanatory diagram showing an outline of assembly of the gas sensor 100. When assembling the gas sensor 100, the rear end side assembly A having the rear end side structure of the gas sensor 100 and the front end side assembly B having the front end side structure are assembled, and the assemblies A and B are assembled. FIG. 4 is a cross-sectional view for explaining the assembly operation of placing the assembly A on the rear end of the assembly B.

  When manufacturing the gas sensor 100, first, the front end side assembly B is assembled. Specifically, the sensor element 10 is disposed on the packing 30 disposed in the metal shell 20. Thereafter, the sealing material 31 is filled in the gap between the metal shell 20 and the sensor element 10, and the insulating member 32 and the metal ring 33 are sequentially disposed on the sealing material 31. And the assembly B is produced by crimping the rear end side of the metal shell 20.

  On the other hand, the rear end side assembly A is assembled. That is, the separator 34 assembled with the first connection terminal 70 and the second connection terminal 80 is arranged together with the grommet 36 in the outer cylinder 40 to assemble the assembly A. Specifically, the first connection terminal 70 and the second connection terminal 80 connected to the lead wire 60 are inserted into the insertion holes 34 a and 34 b of the separator 34, and then the separator 34 is inserted into the step portion 43 of the outer cylinder 40. Make contact. Thereafter, the holding metal fitting 35 is inserted into the gap between the separator 34 and the outer cylinder 40, and the distal end portion 40 a of the outer cylinder 40 is caulked to fix the holding metal fitting 35. Further, the grommet 36 is inserted from the rear end of the outer cylinder 40, and the filter 37 and the protective outer cylinder 38 are disposed at the rear end portion 40b of the outer cylinder 40, respectively, and the filter 37 and the grommet 36 are fixed by crimping. Assembly A is made.

  Then, the gas sensor 100 is assembled by aligning the axes of the assembly A and the assembly B and covering the front end of the outer cylinder 40 of the assembly A over the rear end of the metal shell 20 of the assembly B.

  As shown in FIG. 4, in the rear end side assembly A, the insertion portion 73 of the first connection terminal 70 protrudes from the tip of the outer cylinder 40. Further, in the front end side assembly B, the reduced diameter portion 18 of the sensor element 10 and a part (rear end portion) of the base portion 17 are exposed from the rear end of the metal shell 20. When assembling the assembly A and the assembly B, first, the insertion portion 73 protruding from the assembly A is inserted into the cylindrical hole 10d formed in the sensor element 10 of the assembly B, and the distal end portion of the outer cylinder 40 is moved. Then, cover the rear end of the metal shell 20. At this time, the insertion portion 73 is in contact with the inner surface of the cylindrical hole 10d, whereby the first connection terminal 70 and the inner electrode 10a are electrically connected.

  Moreover, when the front-end | tip part of the outer cylinder 40 is covered on the rear-end part of the main metal fitting 20 as mentioned above, the front-end | tip of the cylindrical part 83 of the 2nd connection terminal 80 with which the assembly A is provided inside the assemblies A and B is as follows. The tubular portion 83 is fitted into the rear end portion of the sensor element 10 in contact with the rear end of the sensor element 10. At this time, the inner surface of the cylindrical portion 83 is in contact with the ring lead portion 16, so that the second connection terminal 80 and the outer electrode 10b are electrically connected.

  FIG. 5 is an explanatory diagram illustrating a state in which the tubular portion 83 of the second connection terminal 80 is fitted into the rear end portion of the sensor element 10. Here, for convenience of illustration, the cylindrical portion 83 shows a cross-sectional view, and the other members show a front view. 5, the outer diameter of the base portion 17 of the sensor element 10 is D1, the outer diameter of the small diameter portion 18a provided at the rear end of the reduced diameter portion 18 is D2, and the cylindrical portion 83 of the second connection terminal 80 is not fitted. The inner diameter of the cylindrical portion 83 when in the state is represented as D3. A relationship of “D2 <D3 <D1” is established between the diameters of these portions. As described above, when the assembly A and the assembly B are fitted, the small-diameter portion 18a having the outer diameter D2 smaller than the inner diameter D3 of the cylindrical portion 83 is fitted into the cylindrical portion 83 at the distal end portion of the cylindrical portion 83. The tip of the cylindrical portion 83 is in contact with the stepped portion 18b. Thereafter, when the assembly A and the assembly B are further fitted, the cylindrical portion 83 follows the stepped portion 18b, and expands the diameter by widening the slit 85 (FIG. 3). It is inserted into. When the tip of the cylindrical portion 83 exceeds the boundary between the reduced diameter portion 18 and the base portion 17, the cylindrical portion 83 is provided at the rear end of the ring lead portion 16 (at the boundary between the reduced diameter portion 18 and the base portion 17. ) To come into contact.

  When the fitting of the assembly A and the assembly B is completed, the tip of the cylindrical portion 83 enters the metal shell 20 and reaches the vicinity of the rear end of the insulating member 32 (see FIG. 1). When the length in the direction of the axis O where the base portion 17 and the cylindrical portion 83 of the sensor element 10 overlap is increased to some extent, the cylindrical portion 83 becomes substantially parallel to the direction of the axis O, and the inner surface of the cylindrical portion 83 and the base portion 17 is in surface contact with the outer surface. In order to obtain a desired degree of overlap between the tubular portion 83 and the sensor element 10 (positional relationship), the assembly position of the sensor element 10 and the second connection terminal 80 in each assembly, the assembly A, and the assembly What is necessary is just to set beforehand the assembly | attachment position between B according to the said desired overlap condition. The entire tubular portion 83 may overlap the rear end portion of the sensor element 10, or only a part of the front end side of the tubular portion 83 may overlap the rear end portion of the sensor element 10.

  FIG. 5 shows a state in which the ring lead portion 16 is exposed at the rear end of the sensor element 10 protruding from the rear end of the metal shell 20. As described above, the ring lead portion 16 is formed so as to extend in the circumferential direction on the outer surface of the sensor element 10 and has a shape extending along a part of the outer periphery. Since the ring lead portion 16 is exposed from the metal shell 20 as described above, when the assemblies A and B are assembled, the position where the ring lead portion 16 is provided is confirmed in advance by visual inspection. Can be adjusted. Thereby, the overlap of the ring lead part 16 and the slit 85 can be suppressed, the ring lead part 16 is provided in a part along the outer periphery of the sensor element 10, and the cylindrical part 83 has the slit 85. Even if it is a structure, the reliability of the connection of the ring lead part 16 and the cylindrical part 83 can be maintained.

  After assembling the assemblies A and B so that the outer cylinder 40 covers up to a predetermined position of the metal shell 20, the outer peripheral surface of the front end portion of the outer cylinder 40 is caulked, and then the metal shell 20 by laser welding or the like. By connecting to the rear end of the gas sensor 100, the gas sensor 100 is obtained.

  According to the gas sensor 100 of the present embodiment configured as described above, the rear end portion of the sensor element 10 is provided with the small-diameter portion 18a having an outer diameter smaller than the inner diameter of the tubular portion 83 when the sensor element 10 is not fitted. Since the cylindrical portion 83 follows the reduced diameter portion 18 of the sensor element 10, the rear end portion of the sensor element 10 can be easily guided into the cylindrical portion 83. The second connection terminal 80 can be easily fitted into the sensor element 10. In general, the sensor element 10 is manufactured by press-molding a powder of a constituent material (for example, yttria-containing zirconia powder) and firing it at a predetermined temperature. In order to provide the reduced diameter portion 18 in the sensor element 10 as in the present embodiment, it is only necessary to change the mold design used for the molding, and it is not necessary to change the manufacturing process.

  In particular, as described above, the operation of fitting the cylindrical portion 83 into the rear end portion of the sensor element 10 is performed simultaneously when the assemblies A and B are assembled, and the cylindrical portion 83 is attached to the sensor element 10. It is difficult to perform while visually confirming the state of being fitted. As in the present embodiment, by providing the sensor element 10 with the reduced diameter portion 18 and guiding the tip of the cylindrical portion 83, the fitting operation of the cylindrical portion 83 into the sensor element 10 can be performed more accurately. Therefore, the reliability of the electrical connection between the second connection terminal 80 and the outer electrode 10b can be maintained.

  Furthermore, according to this embodiment, since the rear end of the external lead portion 10c is disposed on the boundary between the base portion 17 and the reduced diameter portion 18 on the outer surface of the sensor element 10, the outer electrode 10b and the The reliability of the electrical connection between the two connection terminals 80 can be ensured.

  For example, when using the cylindrical part 83 having a C-shaped cross section having the slit 85 as in the present embodiment, after the cylindrical part 83 reaches the base part 17 during assembly, If the amount of overlap with the base portion 17 is insufficient, the diameter of the cylindrical portion 83 on the front end side may be further widened, resulting in a case where the vertical cross section becomes a square shape. In this case, the distal end side of the cylindrical portion 83 is lifted (separated) from the base portion 17 of the sensor element 10. Even in such a case, the electrical connection between the outer electrode 10b and the second connection terminal 80 is ensured by forming the external lead portion 10c at the boundary between the base portion 17 and the reduced diameter portion 18. be able to. That is, even if the distal end side of the cylindrical portion 83 is lifted from the base portion 17 of the sensor element 10, an external lead is provided at a location (a boundary between the base portion 17 and the reduced diameter portion 18) that reliably contacts the second connection terminal 80. Since the portion 10c is provided, the reliability of the electrical connection between the outer electrode 10b and the second connection terminal 80 can be ensured. Since the external lead portion 10c is provided to extend from the boundary between the base portion 17 and the reduced diameter portion 18 to the distal end side, when the cylindrical portion 83 is substantially parallel to the surface of the base portion 17. In the wider range of the external lead portion 10c, electrical connection with the second connection terminal 80 becomes possible.

  Further, since the tip of the cylindrical portion 83 can be inserted into the metal shell 20, even if the rear end portion of the sensor element 10 is shorter than the conventional one, the sensor element 10 and the cylindrical portion 83 are in the direction of the axis O. It is possible to secure a sufficient overlap distance. Therefore, the sensor element 10 can be made shorter (downsized) while maintaining the reliability of the connection between the second connection terminal 80 and the outer electrode 10b, and further downsizing of the entire gas sensor 100 can be achieved. It becomes possible. As a result, by shortening the rear end portion of the sensor element 10, the length of the vertical lead portion 15 (FIG. 2) of the external lead portion 10 c connected to the outer electrode 10 b is shortened, and the inner surface of the sensor element 10 is formed. The formed inner electrode 10a and the wiring connected thereto can be reduced. Therefore, the amount of wiring material (noble metal) used to form the outer electrode 10b, the outer lead portion 10c, or the inner electrode 10a on the surface of the sensor element 10 can be suppressed, and the manufacturing cost can be reduced.

  Furthermore, according to the gas sensor 100 of the present embodiment, the cylindrical portion 83 is provided at the forefront of the second connection terminal 80. As a method for facilitating the fitting of the second connection terminal 80 into the sensor element 10, for example, the distal end of the cylindrical portion of the second connection terminal is an enlarged diameter portion whose diameter increases toward the distal end, and the most advanced portion. A configuration is also possible in which a diameter-enlarged portion having a diameter larger than that of the rear end of the sensor element 10 is provided to guide the rear end of the sensor element into the cylindrical portion. However, when such a configuration is adopted, the diameter-enlarged portion is provided at the tip of the cylindrical portion, which complicates the manufacturing process of the second connection terminal and may cause an increase in cost. According to the present embodiment, it is possible to suppress an increase in cost due to such a complicated manufacturing process.

  In addition, even if the rear end portion of the sensor element 10 is shortened to reduce the size of the sensor element 10, there is no possibility that the metal shell 20 and the second connection terminal 80 are short-circuited. It is not necessary to adjust the diameter of the enlarged diameter portion provided in the two connection terminals 80, and the reliability of the electrical connection between the sensor element 10 and the second connection terminal 80 can be easily maintained.

  The ring lead portion 16 of the external lead portion 10c may be provided over the entire circumference on the outer surface of the sensor element 10, but in this embodiment, it is provided only on a part of the outer periphery. Therefore, the amount of wiring material (noble metal) used to form the external lead portion 10c can be further suppressed. The rear end portion of the external lead portion 10c can be configured such that the width of the vertical lead portion 15 is maintained up to the boundary between the base portion 17 and the reduced diameter portion 18 and the ring lead portion 16 is not provided. Providing the ring lead portion 16 wider than the lead portion 15 makes it easy to ensure the reliability of electrical connection with the tubular portion 83.

C. Second embodiment:
FIG. 6 is a perspective view illustrating an appearance of the sensor element 110 according to the second embodiment. The sensor element 110 is used in place of the sensor element 10 in the same sensor as the gas sensor 100 of the first embodiment. The gas sensor of the second embodiment has the same configuration as that of the first embodiment except for the sensor element. Therefore, common parts are denoted by the same reference numerals, and detailed description thereof is omitted.

  The sensor element 110 has a configuration similar to that of the sensor element 10, but is different from the sensor element 10 only in having a tapered portion 118 as a reduced diameter portion. The tapered portion 118 is formed such that the diameter gradually decreases from the boundary between the base portion 17 and the tapered portion 118 toward the rear end of the sensor element 110. And the outer diameter D4 (refer FIG. 6) of the rear-end part of the taper part 118 becomes smaller than the internal diameter D3 (refer FIG. 5) when the cylindrical part 83 with which the 2nd connection terminal 80 is in a non-fit state. It is formed as follows. Note that the outer diameter of the base portion 17 is D1 as in the first embodiment, and “D4 <D3 <D1” is established. In the sensor element 110, the ring lead portion 16 provided in the external lead portion 10c has a rear end disposed on the boundary between the base portion 17 and the taper portion 118.

  Also in the gas sensor of the second embodiment configured as described above, the same effect as that of the first embodiment can be obtained. That is, it is easy to fit the second connection terminal 80 into the sensor element 110 while suppressing the complexity of the manufacturing process of the second connection terminal 80, and the reliability of the electrical connection between the second connection terminal 80 and the outer electrode 10b. Can be maintained. Moreover, the usage-amount of the wiring material (noble metal) for forming the external lead part 10c and the inner side electrode 10a can be suppressed. In FIG. 6, the ring lead portion 16 extends in the circumferential direction so as to make one round of the outer periphery on the outer surface of the sensor element 110. However, as in the first embodiment, the shape may extend along a part of the outer periphery.

D. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

D1. Modification 1:
The diameter-reduced portion provided on the rear end side of the sensor element can be variously modified, and at least the outer diameter of the rear end is smaller than the inner diameter of the cylindrical portion 83 when not fitted into the base portion 17. Then, the same effect as the first or second embodiment can be obtained. A portion (small diameter portion) having a constant outer diameter smaller than the inner diameter of the cylindrical portion 83 when not fitted, or a portion (tapered portion) having a smaller outer diameter at the rear end portion, Any shape that can guide the cylindrical portion 83 fitted from the rear end side to the base portion 17 without hindrance is acceptable. For example, the reduced diameter portion may have a multistage structure including a plurality of small diameter portions whose outer diameters become smaller toward the rear end side. Or it is good also as a multistage structure provided with several taper part from which the angle of the inclination from which an outer diameter becomes small gradually toward the rear-end part side differs.

D2. Modification 2:
In the gas sensors of the first and second embodiments, the tip of the cylindrical portion 83 of the second connection terminal 80 is inserted into the metal shell 20 and reaches the vicinity of the rear end of the insulating member 32. It is also good. For example, the tip of the cylindrical portion 83 may be configured to be located outside the metal shell 20. Even in this case, the provision of the reduced diameter portion on the rear end side of the sensor element facilitates the fitting of the cylindrical portion 83 into the sensor element, and the boundary between the base portion and the reduced diameter portion of the sensor element. By providing the rear end of the external lead portion 10c, an effect of improving the connection reliability of the electrodes can be obtained similarly. Further, unlike the configuration in which the diameter-enlarged portion described above is provided in the cylindrical portion, the effect of suppressing a short circuit with the metallic shell 20 is obtained even if the tubular portion 83 is sufficiently close to the rear end of the metallic shell 20. be able to.

  Alternatively, in the gas sensor, a gap is provided between the insulating member 32 and the sensor element 10 so that the cylindrical portion 83 can enter from the rear end side, and the tip of the cylindrical portion 83 is deeper and overlaps the insulating member 32. It is good also as inserting even to an area | region. Also in this case, the same effect as the first and second embodiments can be obtained.

D3. Modification 3:
In the first and second embodiments, the reduced diameter portion of the sensor element and the rear end portion of the base portion 17 protrude from the rear end of the metal shell 20 surrounding the sensor element. However, different configurations may be employed. If at least a part of the rear end of the reduced diameter portion 18 of the sensor element protrudes from the rear end of the metal shell 20, even when the base portion 17 on which the ring lead portion 16 is formed does not protrude, The distal end portion of the insertion portion 73 of the first connection terminal 70 can be easily inserted into the cylindrical hole 10d of the sensor element. At this time, the same effect as in the first and second embodiments can be obtained, in which the tip of the cylindrical portion 83 can be easily guided to the outer surface of the base portion 17.

  Here, as in the second embodiment, when the ring lead portion 16 is provided so as to extend over the entire circumference of the base portion 17, the ring lead portion 16 is not projected from the outside of the assembly B because the base portion 17 does not protrude. Even if it is difficult to see, the reliability of the connection can be ensured. That is, the ring lead portion 16 and the tubular portion 83 can be easily connected regardless of the position of the slit 85 and the width of the slit 85 of the tubular portion 83.

  Further, as in the first embodiment, when the ring lead portion 16 has a shape extending along a part of the outer periphery, the length of the ring lead portion 16 extending in the circumferential direction is set to the length of the base portion 17. The length may be more than half of the entire circumference. Or the length which the ring lead part 16 expand | extends in the circumferential direction should just be more than the distance between the slits 85 on the sensor element outer surface when the cylindrical part 83 will be in a fitting state. With such a configuration, even if the ring lead portion 16 is difficult to visually recognize from the outside of the assembly B, the space between the ring lead portion 16 and the tubular portion 83 is not affected by the position of the slit 85 of the tubular portion 83. Can be connected easily.

D4. Modification 4:
In the first and second embodiments, the cylindrical portion 83 is provided at the forefront of the second connection terminal 80, but an enlarged diameter portion may be provided at the tip of the cylindrical portion 83 of the second connection terminal 80. . In order to reduce the size of the sensor element 10, when the rear end portion of the sensor element 10 is shortened and the second connection terminal 80 is inserted into the metal shell 20, the diameter of the expanded portion is set to the sensor element. It is necessary to adjust the diameter of the enlarged-diameter portion so that it does not come into contact with the metal shell while being larger than the diameter of the rear end portion.

D5. Modification 5:
In the first and second embodiments, the gas sensor is an oxygen concentration sensor, but may have a different configuration. The present invention is a sensor having a concentration cell having a pair of electrodes laminated on both surfaces of a solid electrolyte having ion conductivity and generating an electromotive force due to a concentration difference (partial pressure difference) of a specific gas component on each electrode. The same effect can be obtained by applying.

DESCRIPTION OF SYMBOLS 10,110 ... Sensor element 10a ... Inner electrode 10b ... Outer electrode 10c ... External lead part 10d ... Cylindrical hole 11 ... Solid electrolyte body 12 ... Gutter part 13 ... Bottomed part 14 ... Poisoning prevention layer 15 ... Vertical lead part 16 ... Ring Lead part 17 ... Base part 18 ... Reduced diameter part 18a ... Small diameter part 18b ... Step part 20 ... Metal fitting 20a ... Casting part 20b ... Step part 20c ... Hard part 20d ... Male thread part 20f ... End part 30 ... Packing 31 ... Seal Material 32 ... Insulating member 33 ... Metal ring 34 ... Separator 34a, 34b ... Insertion hole 35 ... Holding bracket 36 ... Grommet 37 ... Filter 38 ... Protective outer cylinder 39 ... Second vent hole 40 ... Outer cylinder 40a ... Tip 40b ... Rear End 41 ... First vent hole 43 ... Step part 60 ... Lead wire 62 ... Protector 63 ... Opening 70 ... First connection terminal 71, 81 ... Plate-like base 72, 82 Connecting end portions 73 ... insertion portion 80 ... second connecting terminal 83 ... tubular portion 84 ... support arms 85 ... slit 100 ... gas sensor 118 ... tapered portion

Claims (6)

A cylindrical sensor element that extends in the axial direction, and includes an outer electrode provided on the outer surface of the tip, which is one end in the axial direction, and the other end in the axial direction from the outer electrode. An external lead portion provided to extend to the outer surface on the rear end side that is a portion, and a sensor element,
A cylindrical portion that is elastically deformable in a radial direction, and at least a tip end portion of the cylindrical portion is fitted into an outer surface of a rear end portion of the sensor element, and contacts the external lead portion in the cylindrical portion A terminal,
In a gas sensor for detecting a specific gas component in a gas to be measured, comprising:
The rear end portion of the sensor element has an outer diameter larger than the inner diameter of the cylindrical portion when the sensor element is not fitted into the sensor element, and the cylindrical portion is fitted into the sensor element when the cylindrical portion is fitted into the sensor element. A base portion in contact with the inner surface of the base portion, and a shrinkage formed on the rear end side of the base portion and having an outer diameter on the rear end side that is at least smaller than the inner diameter of the cylindrical portion when in the non-fitted state. With a diameter part,
A gas sensor, wherein a rear end of the external lead portion on the outer surface of the sensor element is disposed on a boundary between the base portion and the reduced diameter portion. The gas sensor according to claim 1, further comprising:
The said cylindrical part is provided in the forefront of the said connection terminal, The gas sensor characterized by the above-mentioned. The gas sensor according to claim 1 or 2, further comprising:
A metal shell that surrounds the sensor element and exposes at least the reduced diameter portion of the sensor element,
A gas sensor, wherein a tip end portion of the cylindrical portion fitted into a rear end portion of the sensor element is disposed in the metal shell. The gas sensor according to claim 1 or 2, further comprising:
A metal shell that surrounds the sensor element and exposes a rear end of the sensor element,
The cylindrical portion has a slit parallel to the axial direction, and is elastically deformable in the radial direction by expanding and contracting the width of the slit.
A ring lead portion that extends to a part of the outer surface of the sensor element along the outer periphery of the sensor element with the boundary between the base portion and the reduced diameter portion as the rear end at the rear end portion of the external lead portion. Prepared,
The sensor element is surrounded by the metal shell such that the ring lead portion is exposed from the metal shell. Gas sensor. The gas sensor according to any one of claims 1 to 4,
The reduced diameter portion is formed between a small diameter portion having a constant outer diameter smaller than an inner diameter of the cylindrical portion when not fitted into the sensor element, and the base portion and the small diameter portion. A gas sensor comprising a stepped portion. The gas sensor according to any one of claims 1 to 4,
The reduced diameter portion is a tapered portion that gradually decreases in outer diameter from the boundary with the base portion toward the rear end of the sensor element.